Rubberized blown asphalt and method for making same



United States Patent 01 3,610,927 RUBBERIZED BLOWN ASPHALT AND METHOD FOR MAKING SAME Frank B. Odasz, J22, (Jody, Wyo., and John R. Hartwig, Bienfait, Saskatchewan, Canada, assignors to Husky Oil Company, Cody, Wy0., a corporation of Delaware No Drawing. Filed June 18, 1959, Ser. No. 821,086

12 (Ilaims. (Cl. 260-285) The present invention relates to asphaltic compositions, and, more particularly, to compositions consisting essentially of asphalt having minor proportions of rubber interblended therewith, or intimately dispersed therein, herein designated rubberized asphalt. The invention provides such asphaltic compositions having novel and highly useful physical and chemical properties and also provides a commercially practical and economical method for producing such compositions and for regulating and controlling the properties thereof.

This application is, in part, a continuation of our co pending application Ser. No. 624,959, filed November 29, 1956, now abandoned. It has heretfore been recognized that by properly interblending a natural or synthetic rubber with an unblown asphalt, a marked change in the physical properties of the asphalt, such as durability, ductibility, adhesion, toughness and tenacity, can be obtained, resulting in a product definitely superior for many uses. It has also been proposed to disperse rubber in blown asphaltic compositions. However, where a blown asphalt has been so used, the physical characteristics of the result-ant product have not heretofore been satisfactory, predictable or readily controllable.

The nature of such dispersions of rubber in asphalt is not fully understood. Microscopic examination of interblends of rubber and unblown asphalt has revealed the presence of discrete particles and threads of the rubber, suggesting that, in part at least, the dispersion is a physical admixture. However, it appears that a substantial portion of the rubber dispersed in the asphalt is more intimately blended therewith, as though dissolved in, or even chemically united with, the asphalt. It appears, more particularly, that the improved properties of the blend are primarily brought about by this more intimate associa tion of the rubber and asphalt molecules, rather than by the less intimate dispersion of discrete particles or threads of the rubber in the asphalt. it has further been observed that where the asphalt-ic constituent does not have an allim'ty for, or capacity to absorb, the rubber in a manner akin to dissolving it, attempts to rubberize such asphalt have generally been unsuccessful.

A striking example of asphalts which do not normally have such an aflinity for, or capacity to thus absorb, the rubber are the conventional, so-called blown asphalts. These blown asphalts normally have chemical characteristics or molecular structures which are considerably different from those of the cracked, straight-run of vacuumreduced asphalts, which have heretofore been successfully rubberized. The blowing operation by which such blown asphalts are produced involves heating an asphalt, usually as an asphalt 1 mx, to a temperature of about 400-450 F and oxidizing the mass by blowing air therethrough.

The result of this oxidation is a change in the nature of the entire mass and the purpose is normally that of producing a harder asphalt of higher softening point, usually of the order of F. or higher. Other physical and chemical characteristics of the asphalt which have generally been changed by this blowing operation include the development of greater resistance to flow and weathering and the development of an apparently more negative allinity of the resultant blown asphalts for the various rubbers with which it has been attempted to blend them.

The increased softening points of these blown asphalts have made it necessary to heat them to a higher temperature in order to render the asphalt sulficien-tly fluid for ready mixing with the rubber, temperatures indeed so high as to cause injury to the rubber before it could be satisfactorily interblended with the hot blown asphalt.

The present invention provides an improved method of producing rubberized blown asphalts, comprising a plurality of cooperating steps by which the beneficial effects of the interblending of rubber with the blown asphalt are readily, economically and moretully attained, resulting in rubberized blown asphalts having novel and highly useful properties and combinations of properties by Which they are especially adapted to a wide range of commercial uses, including paper l-aminants, road building, crack tillers, waterproofing, plastic asphalts, primers, and the like, particularly where the low temperature characteristics of the asphaltic compositions are a major consideration.

By our improved process, the higher soct'tening point of the blown asphalts is no longer a problem and the rubber is intimately interblended therewith without destruction of the desirable properties of the rubber, whether by depolymerization or objectionable copolymerization of the rubber molecules.

In previous attempts to produce rubberized blown asphalts, it has been proposed, for instance, to mix asbestos fibers, or the like, with the blown asphalt in a plastic state and thereafter mix a rubber latex with the resultant plastic asphaltic material. It has also been proposed to mix an aqueous rubber latex with an oil-in-water type emulsion of blown asphalt.

The process and product of our present invention are distinguished from those proposed in that we are here concerned with a rubberized blown asphalt which is substantially free from water and which consists essentially of a dispersion of rubber in blown asphalt without added mineral or vegetable fibers.

It has further been proposed to \mix the latex with unblown asphalt, thereafter blowing the mixture. But to our knowledge, that procedure has not given results satisfactory for our purpose, perhaps due, in part at least, to the subjecting of the rubber to excessive temperatures during the prolonged blowing operation.

We have found that the characteristics of the blown asphalt, prior to rubberizing, and the manner in which it is produced, and also the method by which the rubber is interblended with the asphalt, are of utmost importance and cooperate to produce the desired novel results.

The nature of the base asphalt, i.e., the asphalt used in making the flux to be blown, does not appear to be critical. 'It may, for instance, be a natural asphalt or one produced from petroleum, such as the conventional, so-called cracked, vacuum-reduced or straight-run asphal-ts. Similarly, characteristics of the specific flux oil used is not critical and may be varied over a wide range. Likewise, the blowing temperature and rate of blowing are not critical. Conventional blowing apparatus may be used. However, it is essential that the asphalt flux, prior to blowing, be adjusted to an SFS viscosity within the range of about 40 to about 300 at 210 F. preferably to about 75 to 175 SP5, and that this flux be air blown to a softening point within the range extending from about 80 to about 165 F., more advantageously 125-l50 F. We have found that the softening point to which the flux is blown is of primary importance in determining the characteristics of the resultant rubberized blown asphalt. We have found that where the flux is blown to a softening point in excess of about 165 F., the subsequent interblending with rubber does not bring about the desired change with respect to penetration, ductility and stain properties of the rubberized product, particularly those characteristics at low temperatures. Similarly, where the asphalt flux is not blown to a softening point of at least as high as 80 F., the desired properties of the product are not obtained.

The characteristics, and combinations of characteristics, embodied in the resultant rubberized blown asphaltic compositions, produced in accordance with our present invention, may be varied over a surprising range to meet special requirements, as to (a) softening point temperature, (b) penetration at 77 F., (c) penetration at 32 F., (d) ductility at 77 F., (e) ductility at 392 F. and (f) stain characteristics, by varying the operating conditions and extent of the blowing step and the nature and proportion of the rubber interblended with the resultant blown asphalt, as hereinafter more fully described.

-As previously noted, a second essential feature of our present ,invention is the manner in which the rubber is interblended with the resulting blown asphalt. In accordance'with our present process, this interblending is effected by introducing the rubber in the form of an aqueous latex into a molten body of the blown asphalt. In order to obtain the required more intimate association of the rubber and asphalt molecules, it is essential that the rubber of the latex be quickly, thoroughly and uniformly dispersed in the blown asphalt while the latter is in a molten, highly fluid condition.

'T he normally high melting point of blown asphalts requires that they be highly heated in order to bring them to such highly fluid condition, i.e., to temperatures considerably higher than those which the rubber can withstand. It is equally important, however, that the rubber not be subjected to thermal conditions by which the rubbar is deleteriously affected, i.e., by deploymerization or copolymerization of the rubber molecules to nonelastic materials. Further, the blown asphalt should not be heated to temperatures at which the essential qualities of the blown asphalt are destroyed. Thus the rubberizing of blown asphalts has presented exceptionally difficult problems.

We have found that the desired, intimate interblending of the rubber with blown asphalt can be satisfactorily and economically effected, without injury to either the rubber or the blown asphalt, by introducing the aqueous rubber latex into a flowing, confined body or stream of the blown asphalt, which at the point of such introduction, is at a temperature at which the asphalt is highly fluid, substantially in excess of that at which the rubber'is deleteriously affected, but below that at which the blown asphalt is deleteriously afiected, and such that the latex-water is quickly flashed into steam causing violent agitation, and thereby atomizing and intimately dispersing the rubber solids of the latex in the hot asphalt, as described and claimed in Patent No. 2,921,105. Heat absorbed by this flashing of the latex-water into steam quickly lowers the temperature of the mixture to a safe temperature for the rubber before the rubber can be damaged. The resultant mixture of steam, blown asphalt and rubber is, with advantage, continued through the confining conduit for a brief period to insure uniform dispersion of the rubber 4 solids throughout the asphalt and is then discharged into a vessel providing a free surface to permit disengagement of the steam from the mixture.

Where the resultant hot asphaltic mixture is relatively rapidly cooled, as in pilot plan operation in which relatively small volumes of the rubberized asphalt are involved, we have found it advantageous to stir the mixture vigorously as it cools through the temperature range of about 390 F to 340 F. However, this stirring does not appear to be essential to the obtaining of a satisfactory, homogeneous product, particularly in large-scale commercial operations.

In copending application 'Ser. No. 535,600, filed Sep tember 21, 1955, now Patent No. 2,921,313, of which one of us is the applicant there is described and claimed a process, similar to that described above, which We have found highly efiective for carrying out the interblending step of our present process.

In accordance with the process of the last said copending application, the asphalt, at the point of introduction of the latex, is at a temperaure, so coordinated with the amount of water present in the selected proportion of the latex to be introduced, and the proportions and specific heat characteristics of the asphalt and of the rubber, that the temperature of the mixture is quickly reduced, primarily by evaporation of the latex-water, to below that at which the rubber is deleteriously affected, but above the foaming temperature of the mixture, e.g., not below about 325 F; By this procedure, the interblending and expelling of the latex-water are effected without forming objectionable, persistent foam or froth previously encountered in dewatering asphalt mixtures.

We have found that, where the procedure of the said copending application is used to carry out the interblending step of our present process, the initial temperature of the blown asphalt should be within the range of about 450 to about 600 F., depending upon the amount of latex-water to be evaporated, and that the temperature of the resultant mixture should fall to a temperature not below 325 F. preferably within the range extending from about 350 to about 400 F.

Accordingly, the interblending step of our present process may, with particular advantage, be effected by injecting, or otherwise introducing, the selected rubber latex, at a constant predetermined rate, into a body of the hot blown asphalt flowing at a constant rate as a confined stream, the proportion of latex so introduced being equivalentto the predetermined amount of rubber solids to be incorporated in the blown asphalt.

The temperature of the body of asphalt at the point where the latex is introduced must be sufiiciently high to cause the latex-water to flash into steam upon contact with the asphalt, resulting in vigorous agitation and thereby efiecting rapid dispersion and interblending of the rubber with the hot asphalt. The absorption of heat by the evaporation of the latex-water causes a sudden reduction in the temperature of the mixture to below that at which the rubber is deleteriously aiiected but not lower than the temperature at which the particular asphalt remains highly fluid.

As above indicated, the initial temperature of the asphalt should generally be within the range from about 450 to about 600 F., but should not exceed that at which the asphalt is injured. Usually, the initial temperature of the asphalt should be as high as permissible with due consideration of the other requirements previously noted and, particularly, the proportion of latex-water to be evaporated. The proportion of water present in the latex used may be varied over a considerable range and may, with advantage, be so coordinated with the initial temperature of the asphalt as to produce the desired temperature drop. I

By this method of interblending, the dispersing of the rubber in the molten blown asphalt and the reduction in temperature of the mixture are accomplished so rapidly U that while full advantage is taken of the high temperature in promoting the desired intimate interblending, the period of time during which the rubber is subjected to such high temperature is so brief as to avoid damagingthe rubber.

The resultant mixture of asphalt, rubber and steam, still in a highly fluid condition, is continued as a confined flowing stream for a period sufficient to assure uniform dispersion of the rubber throughout the asphalt and the mixture is then passed to an open vessel, or other chamber, adapted to the disengaging of the steam from the mixture. In order to expedite this disengagement of the steam, it is especially desirable, that, in accordance with the above-noted copending application Ser. No. 535,600, the initial temperature of the asphalt should be so coordinated with the amount of latex-water to be vaporized that the temperature of the mixture not fall below its foaming temperature, preferably not below 325 F.

Though the previously described methods of carrying out the interblending step have been found to give especially satisfactory results, other methods of carrying out this step, which involve rapid mixing of the rubber with the blown asphalt while the latter is in a molten, highly fluid condition preferably at a temperature in excess of about 450 F., and a sudden reduction of the temperature to below that at which the rubber is injured, may be employed.

In conjunction with this interblending step just described, We have found that the manner in which the blown asphalt is prepared profoundly affects the characteristics of the resultant rubberized blown asphalt. We have further found that the type and proportion of latex used markedly influence the characteristics of the product.

We have, with particular advantage, used aqueous latices of synthetic rubbers of the polychloroprene type and of the GRS (butadiene-styrene) type in proportions within a range equivalent to about 0.5% to about of rubber solids, based on the Weight of the asphalt, and the invention will be more particularly illustrated with reference to those particular synthetic rubbers. How ever, it will be understood that the invention also contemplates the use of the natural or synthetic rubber in latex form, and even in excess of 5% rubber solids.

For producing rubberized blown asphalt compositions especially suited for use as joint or crack fillers and the like, we have, with particular advantage, interblended with the blown asphalt synthetic rubbers of the type just noted in proportions Within the range of about 2.5% to about 4.5%. Similarly, in producing rubberized blown asphaltic compositions especially suited for use as paper laminants, we have found proportions of these synthetic rubbers within the range of about 0.5 to about 3% to be particularly advantageous.

As we have previously noted, the usual purpose of air blowing an asphalt is to increase its hardness, to increase its softening point and reduce penetration at ordinary temperatures, at 77 F., for instance. However, we are here particularly concerned with the production of an air blown asphalt especially amenable to intcrblending with rubber for the production of rubberized asphalts having novel and highly desirable low temperature characteristics, as indicated, for instance by penetration values at 32 F. and ductility at 392 F. These characteristics have not heretofore been predictable from the softening point and penetrations at normal temperatures of the blown asphalt constituent. To our knowledge, there has not heretofore been available a satisfactory method or dependable criteria for producing rubberized blown asphalt compositions of the desired low temperature properties.

We have found, as previously noted, that asphalts especially suited for our purpose are produced by airblowing an asphalt flux having a viscosity within the range of about 40 to about 300 SFS at 210 F. to a softening point not in excess of about 165 F. and not less than about F. The preparation of the flux to be blown is subject to considerable variation as to nature of the flux oil and characteristics and origin of the base asphalt, as previously noted herein. In the specific examples hereinafter shown, as illustrations of our invention, we have used a petroleum vacuum distilled asphalt, derived from a Wyoming Block crude, and as the flux oil, we have used a viscous petroleum oil fraction such as conventionally used for that purpose, namely, one having an A.P.I. gravity within the range of 11-20. The proportion of the flux oil added will, of course, be determined by the nature of the base asphalt and the desired fiux viscosity.

By varying the initial flux viscosity and the softening point to which the flux is blown, within the above prescribed ranges, marked variation in the properties of the rubberized blown asphalt may be effected, as hereinafter illustrated. Another condition materially affecting the characteristics of the rubberized product is Whether or not a blowing catalyst is used.

In accordance with the process of our present application, the blowing operation is carried on in the presence of a catalytic proportion of sulfur, advantageous within the range of about 0.5% to about 5%. We have, with particular advantage, used about 3% of sulfur, by weight.v

In our related copending applications 085 and Serial No. 821,087, filed concurrently herewith, the blowing step is carried out in the absence of a blowing catalyst and in the presence of P 0 catalyst, respectively.

The way in which the characteristics and combinations of properties of the resultant rubberized blown asphalt may be varied in accordance with our present process is illustrated by a series of runs, the characteristics of the products of which are set forth in the following Table I. For purposes of more accurate comparison, the variables in the respective operations have been restricted to a minimum. It will be understood, however, that the in- Vention is not limited in scope to the particular conditions and products of this series of runs.

Ineach case, the base asphalt was "a conventional vacuum reduced Wyoming petroleum asphalt having a penetration of about 265 dmm. at 77 P. out to the indicated flux viscosity by incorporating therein, before blowing, a gas oil of an A.P.I. viscosity, of 11.4. The blowing temperature in each case was 450 F. and the blowing was continued, in the presence of 3% sulfur, until the softening points indicated in Table I were obtained. Separate portions of each batch of the blown asphalts were then rubberized by interblending therewith proportions of polychloroprene marked as Neoprene latex 735 and proportions of GRS2006 (butadienestyrene) rubber latex, respectively, equivalent to the percent-ages of rubber solids set forth in Table I, and the physical characteristics of the unrubberized blown asphalt and of the respective rubberized blown asphalts produced therefrom, as determined by conventional methods, were as recorded. The stain properties of the rubberized blown asphalts are also included in the tabulation.

In each of the interblending operations, the latex was rapidly mixed with the blown asphalt preheated to a temperature at which it was in a molten highly fluid condition and such that the latex-water was quickly flashed into steam causing intimate dispersion of the rubber solids in the hot asphalt and lowering the'temperature of the dispersion, as hereinbefore described.

Serial No. 821,-

TABLE 1 Rubber Flux Increase in S.P., F. Penetration at 77 F. Penetration at 32 F. Blown vis. at Blown Asphalt 210 F. to S.P.

Polychloroprene GRS None Polychloroprene GRS None Polychloroprene GRS 42 101 11 17 V 12 29 300 245 228 133 127 V 86 78 S 70 61 42 125 5 12 20 43 87 82 77 77 57 42 42 47 42 39 42 150 18 40 30 53 45 45 45 40 42 29 31 29 27 29 111 100 7 11 20 289 238 213 192 161 71 59 65 58 48 111 127 3 9 15 29 76 70 73 65 47 29 28 28 23 111 152 7 16 15 31 36 36 40 36 18 20 23 19 20 302 110 9 15 15 22 149 133 122 124 97 37 41 35 34 302 125 9 21 14 21 68 62 65 56 54 18 21 22 19 19 302 153 10 15 7 27 30 29 32 27 27 15 12 13 14 14 Rubber Duetilit'y at 77 F. Ductility at 39.2 F. Stain Blown asphalt Polyehloroprene GRS Polychloroprene GRS Polychloroprene GRS None None None As appears from the foregoing tabulation, the softening point of the rubberized blown asphalt is generally increased as the proportion of rubber interblended therewith is increased. However, we have found that other variables in the production of the blown asphalt materially affect the rate of this increase independently of the 40 proportion of rubber interblended therewith. Usually, it has been found that this rate of increase of softening point may be increased by decreasing flux viscosity. Also, an increase in the softening point to which the flux is blown tends to increase the effectiveness of the rubber in increasing the softening point of the rubberized product.

Where sulfur is used as the blowing catalyst, we have found that its rate of increase in the softening point, as the proportion of rubber is increased, is materially less than obtained where no blowing catalyst or a P 0 catalyst is used. Polychloroprene rubber has been found to increase the softening point less than GRS rubber.

Penetration of the rubberized asphalt at 77 F. is influenced greatly by the initial flux viscosity and the softening point to which it is blown and generally decreases as the proportion of rubber is increased. The lower the softening point to which the flux is blown the greater the rate of decrease in penetration of the rubberized asphalt at 77 F. as the proportion of rubber is increased.

A surprising great reduction in penetration at 77 F. is obtained where a flux, having a viscosity of about 100 or lower, is blown in the presence of sulfur catalyst to a softening point of about 100 F. The increase in the proportion of rubber has little effect upon the penetration at 77 F. where the 'asphalt'fiux is blown to softening points of 125-150 F,

The penetration of the rubberized asphalt at 32 F. is influenced largely by the viscosity of the blowing flux and the softening point to which it is blown. The interblending of rubber therewith has little or no effect on low-temperature penetration. In general, as the softening point to which the flux is blown is increased, the low-temperature penetration decreases sharply. The lower the viscosity of the flux, within the prescribed range, the higher the penetration of the rubberized asphalt at 32 F.

Ductility of the rubberized asphalt at 77 F. has usually been found to increase as the proportion of rubber is increased. An exception to this rule is where a low viscosity flux is blown to a high softening point, in which case rubberizing has little or no influence on ductility at 77 F. We have further found that where a flux of a viscosity of 106 SFS at 210 F., is blown to a softening point of F. the interblending of rubber therewith will cause a sharp drop in ductility at 77 F. We have found, in general, that where sulfur is used as the blowing catalyst, in accordance with our present process, the resultant rubberized asphalts are of greater ductility than where no blowing catalyst or a P 0 blowing catalyst is used.

Of particular interest is the low temperature ductility of the rubberized asphalt. We have found, in general that rubberized asphalts produced from a flux blown in the presence of sulfur catalyst are of lower ductility at 39.2 F. than those produced using either no catalyst or a P 0 blowing catalyst. Also, the increasing of the proportion of rubber interbleuded therewith has only a minor effect on low temperature ductility of the resultant rubberized product.

With respect to the stain properties of the rubberized asphalt, which are of particular interest where the product is to be used as a paper laminant, or the like, of primary importance is the softening point to which the asphalt is blown. Also, both GRS rubber and neoprene rubber have been found materially to influence this char acteristic of the product, the stain characteristic inaterially decreasing as the proportion of the rubber interblended therewith is increased.

However, we have found that this decrease in stain value is greatest where the blowing of the asphalt flux is stopped while the softening point is near the lower limit of the prescribed range i.e., about 80400 F. The rate of decrease in stain value as the proportion of rubber is increased is greatest up to the point where the proportion of rubber is about 2% and thereafter the rate of decrease in stain value diminishes as the proportion of rubber is further increased.

The following examples are given further to illustrate 9 the unique and highly useful products which may be produced in accordance with the present invention.

Example I A rubberized asphaltic composition especially adapted for use as an undersealing asphalt, and which meets the specifications prescribed for Undersealing Asphalt Bureau of Reclamation Specification 617-C-30 isproduced by air blowing at 450 F. a 110 viscosity flux, SFS at 210 F.,- produced by fluxing an asphalt having a penetration of 265 dmm. at 77 F. with a gas oil having an A.P.I. gravity of 11.4, in the presence of 3% sulfur catalyst, to a softening point of 127 F. and rubberizing the resultant blown asphalt with 3% of GRS- 2006 synthetic rubber by the procedure previouslydescribed herein. ized asphalt are set forth in the following tabulation, the values of the Specification 617-C-30, referred to above, being included for ready comparison:

Further products which, for instance, are especially adapted to use in lining of septic tanks are produced by blowing at 450 F. a flux having a viscosity of 42 SFS at 210 F. composed of the above described asphalt and a gas oil of 11.8 A.P.I. gravity. This flux, to which 3% of sulfur catalyst has been added, is blown to a softening point of 150 F. and rubberized as hereinbefore described. In product A, the latex used in rubberizing the blown asphalt was GRS-2006 and in product B the rubber latex was Neoprene 735.

The characteristics of the resultant products are set forth in the following tabulation in which there has been included, for ready reference, the commercial specification for asphaltic compositions intended for the aboveindicated use:

TABLE III Specifl- Product A Product B cation Softening point, F 185210 203 190 en. at 77 F 25-50 42 44 Pen. at 32 F 20+ 29 29 100- 71 94 3+ 11.2 15

The softening point, penetration and ductility values given herein were determined by established methods, the penetration at 77 F. being determined for 100 gms./5 secs, those at 115 F. being determined for 50 gms./S secs., those at 32 F. being determined for 200 gms./60 sees. and ductilities having been determined at 5 ems/min.

The stain tests were run by placing a sample of the composition to be tested in a ring, such as used for determining softening points, care being taken to remove all asphalt from the outside of the ring. The ring is then placed on a number 42 Whatman filter paper in a forced circulation oven and allowed to remain there for 24 hours at 75 C. The sum of the largest and smallest diameters, expressed in millimeters, of the stain produced on the filter paper is reported as the stain value.

Each of these products has its own unique advantages. We have found, however, that the polychloroprene rubber is more easily handled and has better stability at high temperatures. However, GRS rubber has been found The properties of the resultant rubber- '10 superior with respect to low temperature ductility of the asphaltic composition.

As previously noted, our present process is not restricted to the use of any particular polychloroprene rubber or to any particular copo-lymer of butadienstyrene, such as the GRS-2006 of thepreceding examples. It is applicable to copolymers of styrene and butadiene in any proportions. Further, in the broader aspectof the invention, the proportion of rubber solids dispersed in the blown asphalt may be varied over a range extending from about 0.1% to about 10% by weight.

We claim:

1. The method of producing rubberized asphaltic compositions comprising the following steps, air blowing an asphalt flux having a viscosity within the range extending from about 40 to about 300 SFS, at 210 F., and with which there is admixed a small, catalytically effective proportion of sulfur, to a softening point within the range extending from about F. to about 165 F. and interblending the resultant blown asphalt with a rubber selected from the group consisting of natural rubber, polychloroprene rubber and the copolymers of butadiene and styrene by introducing the rubber in the form of an aqueous latex into a molten highly fluid body of the blown asphalt at a point at which the asphalt is at a temperature such that the water con-tent of the latex is flashed into steam upon contact with the asphalt thereby vigorously agitating the asphalt and quickly dispersing the rubber therein and suddenly lowering the temperature of the resultant mixture to below that at which the rubber is deleteriously affected.

2. The process of claim 1 in which the latex is introduced into a confined flowing stream of the hot asphalt and the resultant mixture is continued as a confined flowing stream for a period sufl'icient to insure uniform dispersion of the rubber through the asphalt and is then discharged into an open vessel for disengaging the steam from the mixture.

3. The process of claim 2 in which the temperature of the asphalt at the point of contact with the latex is within the range of 450 F. to 600 F. and this tempera ture is reduced to within the range of 350 to 400 F.

upon contact with the latex.

4. The process of claim 1 in which the viscosity of the flux prior to blowing is within the range of 75 to 175 SFS, at 210 F.

5. The process of claim 1 in which the flux is blown to a softening point within the range of to F.

6. The process of claim 1 in which the proportion of rubber solid interblended with the asphalt is within the range of 0.5% to 5% by weight.

7. Method of producing rubberized asphaltic compositions comprising the following steps, air blowing an asphalt flux having a viscosity within the range extending from about 40 to about 300 SFS, at 210 F., and in which there is incorporated a catalytic proportion of sulfur, to a softening point within the range extending from about 80 F. to about F. and interblending the resultant blown asphalt with polychloroprene by introducing the polymers in the form of an aqueous latex into a molten highly fluid body of. the blown asphalt at a point at which the asphalt is at a temperature such that the water content of the latex is flashed into steam upon contact with the asphalt thereby vigorously agitating the asphalt and quickly dispersing the rubber therein and suddenly lowering the temperature of the resultant mixture to below that at which the rubber is deleteriously affected.

8. The process of claim 7 in which the latex is introduced into aconfined flowing stream of the hot asphalt and the resultant mixture is continued as a confined flowing stream for a period suflicient to insure uniform dispersion of the rubber through the asphalt and is then discharged into an open vessel for disengaging the steam, from themixture.

' 9. The process of claim 8 in which the temperature of the asphalt at the point of contact with'the latex is within the range of 450 F. to 600 F. and this temperature is to a softening point within the range of 125 to 150 F.

12. The process of claim 7 in which the proportion of rubber solid interblended with the asphalt is within the range of 0.5% to 5% by weight.

References Cited in the file of this patent UNITED STATES PATENTS 1,881,436 Fischer Oct. 11, 1932 5 2,578,001 Cubberley et al. Dec. 11, 1951 2,686,166 Taylor Aug. 10, 1954 2,830,963 7 Trailer et.al.. Apr. 15, 1958 2,841,060 Coppage July 1, 1958 10 2,921,105 Benson Jan. 12, 1960 2,921,313 'OdasZ Jan; 12, 1960 OTHER REFERENCES UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent No. 3,010,927 November 28, 1961 Frank B Odasz Jr, et a1,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 23 for "heretfore'f read heretofore line 26, for "ductibility" read ductility column 5, lines 45 and 46, for the use of the natural or synthetic rubber in latex form and even in excess of 5% rubber solids" read the use of natural rubber in latex form and even in excess of 5% of the natural or synthetic rubber solids column 12 line 15, for "(1936)" read (1956) Signed and sealed this 24th'day of April 1962 (SEAL) Attest:

ESTON G JOHNSON DAVID L. LADD Attesting Officer Commissioner of Patents 

1. THE METHOD OF PRODUCING RUBBERIZED ASPHALTIC COMPOSITIONS COMPRISING THE FOLLOWING STEPS, AIR BLOWING AN ASPHALT FLUX HAVING A VISCOSITY WITHIN THE RANGE EXTENDING FROM ABOUT 40 TO ABOUT 300 SFS, AT 210*F., AND WITH WHICH THERE IS ADMIXED A SMALL, CATALYTICALLY EFFECTIVE PROPORTION OF SULFUR, TO A SOFTENING POINT WITHIN THE RANGE EXTENDING FROM ABOUT 80*F. TO ABOUT 165*F. AND INTERBLENDING THE RESULTANT BLOWN ASPHALT WITH A RUBBER SELECTED FROM THE GROUP CONSISTING OF NATURAL RUBBER, POLYCHLOROPRENE RUBBER AND THE COPOLYMERS OF BUTADIENE AND STYRENE BY INTRODUCING THE RUBBER IN THE FORM OF AN AQUEOUS LATEX INTO A MOLTEN HIGHLY FLUID BODY OF THE BLOWN ASPHALT AT A POINT AT WHICH THE ASPHALT IS AT A TEMPERATURE SUCH THAT THE WATER CONTENT OF THE LATEX IS FLASHED INTO STEAM UPON CONTACT WITH THE ASPHALT THEREBY VIGOROUSLY AGITATING THE ASPHALT AND QUICKLY DISPERSING THE RUBBER THEREIN AND SUDDENLY LOWERING THE TEMPERATURE OF THE RESULTANT MIXTURE TO BELOW THAT AT WHICH THE RUBBER IS DELETERIOUSLY AFFECTED. 